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Variation in Response of Norway Maple Cultivars to Verticillium dahliae. A. M. Townsend, Research Geneticist, U.S. National Arboretum, USDA-ARS, Washington, DC 20002. L. R. Schreiber, T. J. Hall, and S. E. Bentz. Research Plant Pathologist, Former Research Associate, USDA-ARS Nursery Crops Research Laboratory, Delaware, OH 43015; and Horticulturist, U.S. National Arboretum, USDA-ARS, Washington, DC 20002. Plant Dis. 74:44-46. Accepted for publication 16 July 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/PD-74-0044.

Significant variation in foliar symptoms and crown dieback was observed over 16 mo among 13 cultivars of grafted Norway maples after stem inoculation with Verticillium dahliae. Cultivars Jade Glen and Parkway showed the fewest symptoms and Crimson King and Greenlace the most, with wide variation among the other cultivars. In a second study, six of the same 13 cultivars were propagated on their own roots and root-inoculated with the fungus. Crimson King and Greenlace again showed high susceptibility, with high mortality (as much as 80%) and/or incidence of foliar symptoms. The cultivars expressing the greatest tolerance (fewest symptoms and lowest mortality) to root inoculation were also the most tolerant of stem inoculation.